What is the primary IM site for injection in neonates due to its muscle mass?

The vastus lateralis is the primary intramuscular injection site for neonates primarily due to its relative muscle mass and accessibility. This site is located on the lateral aspect of the thigh, which is well-developed even in neonates, making it safe for injections without the risk of nerve or major blood vessel injury.

In neonates, the muscle mass in other areas, such as the deltoid, is less developed, which can lead to a higher risk of injury during injection. The dorsogluteal site, commonly used in older children and adults, is avoided in neonates due to the proximity to the sciatic nerve and the underdevelopment of gluteal muscles, posing a potential risk of injury. While the rectus femoris can also be used, it is not as preferred as the vastus lateralis because it carries more risks of local reactions and discomfort. Therefore, the vastus lateralis remains the most suitable and recommended site for intramuscular injections in neonates.